Rigging is affecting both arms
Bone.008 does not respect naming conventions for mirroring:

Names on right part should finish with &quot;.R&quot; or &quot;.Right&quot; (for instance) to be recognized when parenting to bones.
In more details, the documentation:

Examples of valid separators:
(nothing): handLeft –&gt; handRight

“_” (underscore): hand_L –&gt; hand_R

“.” (dot): hand.l –&gt; hand.r

“-” (dash): hand-l –&gt; hand-r

” ” (space): hand LEFT –&gt; hand RIGHT